docbook: resolve conflict in spack env view (#35682)

If the docbook packages
- docbook-xml
- docbook-xsl

are installed in a spack environment view the catalog files will be in
conflict in the view directory. This PR resolves that by adding an
appropriate prefix to each catalog name so that they are unique in the
view. The resulting XML_CATALOG_FILES environment variable will then be
able to point to both of them.

var/spack/repos/builtin/packages/docbook-xml/package.py

@@ -26,7 +26,7 @@ def install(self, spec, prefix):
 
     @property
     def catalog(self):
-        return join_path(self.prefix, "catalog")
+        return join_path(self.prefix, "xml-catalog")
 
     @run_after("install")
     def config_docbook(self):

var/spack/repos/builtin/packages/docbook-xsl/package.py

@@ -29,7 +29,7 @@ def install(self, spec, prefix):
 
     @property
     def catalog(self):
-        return join_path(self.prefix, "catalog")
+        return join_path(self.prefix, "xsl-catalog")
 
     @run_after("install")
     def config_docbook(self):